Frequency Hopping for Random Access

ABSTRACT

A user equipment configured for use in a wireless communication system is configured for transmitting a random access preamble signal. The wireless communication device in particular is configured to generate a random access preamble signal that comprises multiple symbol groups, with each symbol group on a single tone during a different time resource, according to a frequency hopping pattern that hops the random access preamble signal from at least one of the symbols groups to an adjacent symbol group over a fixed frequency distance and hops the random access preamble signal from at least one of the symbols groups to an adjacent symbol group over a pseudo random frequency distance. Each symbol group comprises one or more symbols. The user equipment is also configured to transmit the random access preamble signal.

RELATED APPLICATIONS

This application claims priority to U.S. Provisional patent ApplicationSer. No. 62/288,436 filed 29 Jan. 2016, and U.S. Provisional patentApplication Ser. No. 62/288,633 filed 29 Jan. 2016, the entire contentsof which are incorporated herein by reference.

BACKGROUND

The Networked Society and Internet of Things (IoT) are associated withnew requirements on cellular networks, e.g. with respect to device cost,battery lifetime and coverage. To drive down device and module cost,using a system-on-a-chip (SoC) solution with integrated power amplifier(PA) is highly desirable. However, it is feasible for the currentstate-of-the-art PA technology to allow 20-23 dBm transmit power whenthe PA is integrated to SoC. This constraint limits uplink “coverage”,which is related to how much the path loss is allowed between the userterminal and base station. To maximize the coverage achievable by anintegrated PA, it is necessary to reduce PA backoff. PA packoff isneeded when the communication signal has non-unity peak-to-average powerratio (PAPR). The higher the PAPR is, the higher PA backoff required.Higher PA backoff also gives rise to lower PA efficiency, and thus lowerdevice battery life time. Thus, for wireless IoT and other technologies,designing an uplink communication signal that has as low PAPR aspossible is critically important for achieving the performanceobjectives concerning device cost, battery lifetime and coverage.

3GPP is standardizing Narrowband IoT (NB-IoT) technologies. There isstrong support from the existing LTE eco-system (vendors and operators)for evolving existing LTE specifications to include the desired NB IoTfeatures. LTE uplink however is based on single-carrierfrequency-division multiple-access (SC-FDMA) modulation for the uplinkdata and control channels, and Zadoff-Chu signal for random access. Dueat least in part to the PAPR properties of these signals, there remainsa need for improvement to uplink access.

SUMMARY

A user equipment is configured for use in a wireless communicationsystem for transmitting a random access preamble signal. The userequipment comprises processing circuitry and radio circuitry, wherebythe user equipment is configured to generate a random access preamblesignal that comprises multiple symbol groups, with each symbol group ona single tone during a different time resource, according to a frequencyhopping pattern that hops the random access preamble signal from atleast one of the symbols groups to an adjacent symbol group over a fixedfrequency distance and hops the random access preamble signal from atleast one of the symbols groups to an adjacent symbol group over apseudo random frequency distance. Each symbol group in the random accesspreamble signal comprises one or more symbols. The user equipment isalso configured to transmit the random access preamble signal.

In some embodiments, the user equipment is configured to randomly selecta single tone on which to transmit a first one of the multiple symbolgroups, and select the single tones on which to respectively transmitsubsequent ones of the multiple symbol groups according to the frequencyhopping pattern.

Embodiments herein also include a radio network node (e.g., a basestation) configured for use in a wireless communication system. Theradio network node comprises processing circuitry and radio circuitry,whereby the radio network node is configured to receive a signal from auser equipment. The radio network node is configured to process thereceived signal in an attempt to detect a random access preamble signalthat comprises multiple symbol groups, with each of the symbol groups ona single tone during a different time resource, according to a frequencyhopping pattern that hops the random access preamble signal from atleast one of the symbols groups to an adjacent symbol group over a fixedfrequency distance and hops the random access preamble signal from atleast one of the symbols groups to an adjacent symbol group over apseudo random frequency distance. Each symbol group in the random accesspreamble signal comprises one or more symbols.

In some embodiments, the radio network node is further configured toreceive one or more other signals from one or more other userequipments, and process the one or more other signals in an attempt todetect one or more other random access preamble signals multiplexed infrequency with the random access preamble signal, according to differentfrequency hopping patterns.

In some embodiments, the pseudo random frequency distance is a functionof: f_(hop)(i)=(f_(hop)(i−1)+(Σ_(k=i*10+1)^(i*10+9)c(k)*2^(k−(i*10+1)))mod(N_(b) ^(sc)−1)+1)mod N_(b) ^(sc),wherein

${i = \frac{t}{T}},$

wherein t is a symbol group index, wherein the random access preamblesignal hops a pseudo random frequency distance every T symbol groups,wherein N_(b) ^(sc) is a number of tones within which hopping is definedfor the random access preamble signal, and c(k) is a pseudo randomsequence. In other embodiments, the pseudo random frequency distance isa function of: f_(hop)(i)=(f_(hop)(i−1)+(Σ_(k=i*10+1)^(i*10+9)c(k)*2^(k−(i*10+1)))mod(N_(b) ^(sc)−1)+1)mod N_(b) ^(sc)wherein N_(b) ^(sc) is a number of tones within which hopping is definedfor the random access preamble signal, wherein c(k) is a pseudo randomsequence, and wherein i=0, 1, 2, . . . is an index of consecutive pseudorandom frequency hops in the frequency hopping pattern. In either orboth of these embodiments, the pseudo random sequence c(k) may comprisea sequence of length M_(PN), where k=0, 1, . . . , M_(PN)−1, and isdefined by

c(k)=(x ₁(k+N _(C))+x ₂(k+N _(C))mod 2

x ₁(k+31)=(x ₁(k+3)+(k))mod 2

x ₂(k+31)=(x ₂(k+3)+x ₂(k+2)+x ₂(k+1)+x ₂(k))mod 2

where

${N_{C} = 1600},{{x_{1}(0)} = 1},{{x_{1}(k)} = 0},{k = 1},2,\ldots \mspace{11mu},30,{c_{init} = {\sum\limits_{i = 0}^{30}{{x_{2}(i)} \cdot 2^{i}}}},$

and c_(init)=N_(ID) ^(Ncell), and N_(ID) ^(cell)=3N_(ID) ⁽¹⁾+N_(ID) ⁽²⁾,where N_(ID) ^(cell) is a physical-layer cell identity.

In any of the above embodiments, the pseudo random frequency distancemay be a function of a cell identity (e.g., a Narrowband physical layercell identity).

Alternatively or additionally, the fixed frequency distance may comprisea frequency distance of a single tone.

In any of the above embodiments, each symbol group in the random accesspreamble signal may comprise a cyclic prefix and two or more symbols.

In some embodiments, each symbol group in the random access preamblesignal comprises a cyclic prefix and five identical symbols.

In some embodiments, the frequency hopping pattern hops the randomaccess preamble signal from at least one of the symbols groups to anadjacent symbol group over a fixed frequency distance in a directionthat depends on a frequency location of the at least one of the symbolgroups.

Alternatively or additionally, the frequency hopping pattern hops therandom access preamble signal across a bandwidth of a random accesschannel, such that the multiple symbol groups span the bandwidth of therandom access channel.

In any of the above embodiments, each of the different time resourcesmay comprise a single-carrier frequency-division multiple-access(SC-FDMA) symbol group interval. Alternatively or additionally, each ofthe single tones on which the symbol groups are generated may be asingle-carrier frequency-division multiple-access (SC-FDMA) subcarrier.

In some embodiments, the user equipment is a narrowband Internet ofThings (NB-IoT) device.

In one or more embodiments, the random access preamble signal istransmitted over a narrowband Physical Random Access Channel, NB-PRACH.

Embodiments also include a network node for use in a wirelesscommunication system for configuring a user equipment to transmit arandom access preamble signal comprising multiple symbol groups, eachsymbol group comprising one or more symbols. The network node isconfigured to generate configuration information indicating one or moreparameters for a frequency hopping pattern according to which the userequipment is to generate each of the symbol groups on a single toneduring a different time resource, wherein the frequency hopping patternhops the random access preamble signal from at least one of the symbolsgroups to an adjacent symbol group over a fixed frequency distance andhops the random access preamble signal from at least one of the symbolsgroups to an adjacent symbol group over a pseudo random frequencydistance. The network node is also configured to transmit theconfiguration information to the user equipment.

Embodiments herein further include corresponding methods and computerprogram products.

According to one or more particular embodiments, a random accesspreamble signal is a signal is designed for the physical random accesschannel (PRACH) of NB-IoT. The new PRACH signal is single tone based andhas extremely low PAPR, and thus reduces the need for PA backoff to thegreatest extent and maximizes PA efficiency. The new PRACH signal iscompatible with SC-FDMA and orthogonal frequency-divisionmultiple-access (OFDMA) as in any OFDM symbol interval, the new PRACHsignal looks like an OFDM signal of one single subcarrier. Note that fora single subcarrier signal, the OFDM signal is identical to the SC-FDMAsignal. Further, hopping patterns are carefully designed such that (1)accurate time-of-arrival estimation can be performed by the basestation, (2) the frequency resources can be fully utilized by PRACHwhile maintaining orthogonality of different preambles.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a wireless communication system thatincludes a wireless communication device and a radio network nodeaccording to one or more embodiments.

FIG. 2 is a block diagram illustrating an example of a frequency hoppingpattern according to one or more embodiments.

FIG. 3 is a block diagram illustrating an example of a frequency hoppingpattern according to one or more other embodiments.

FIG. 4 is a block diagram illustrating an example of multiplexing offrequency hopping patterns within an 12-tone band, according to one ormore embodiments.

FIG. 5 is a block diagram illustrating an example of multiplexing offrequency hopping patterns within an 12-tone band, according to one ormore other embodiments.

FIG. 6 is a line graph illustrating performance of time-of-arrivalestimation for random access preamble signals with differenttransmission bandwidths according to some embodiments.

FIG. 7 is a block diagram illustrating configuration of multipledifferent random access channel bands with different numbers of tonesaccording to one or more embodiments.

FIG. 8 is a block diagram illustrating an example of multiplexing offrequency hopping patterns within an 8-tone band, according to one ormore embodiments.

FIG. 9 is a block diagram illustrating an example of multiplexing offrequency hopping patterns within an 8-tone band, according to one ormore other embodiments.

FIG. 10 is a call flow diagram illustrating steps of a random accessprocedure according to one or more embodiments.

FIG. 11 is a timing diagram illustrating transmission of a random accesspreamble according to one or more embodiments.

FIG. 12 is a block diagram illustrating a symbol group according to oneor more embodiments.

FIG. 13 is a block diagram illustrating a particular example of a symbolgroup according to some embodiments.

FIGS. 14A-14B are graphs illustrating time of arrival performance forafrequency hopping pattern that employs two fixed size hopping distances.

FIGS. 14C-14D are graphs illustrating time of arrival performance forafrequency hopping pattern that employs a fixed size hopping distance aswell as a pseudo random hopping distance according to one or moreembodiments.

FIGS. 15A-15F are graphs illustrating time of arrival performance forafrequency hopping pattern that employs a fixed size hopping distance aswell as a pseudo random hopping distance within different hopping rangesand for different preamble lengths, according to some embodiments.

FIG. 16A is a logic flow diagram of a method performed by a wirelesscommunication device according to some embodiments.

FIG. 16B is a logic flow diagram of a method performed by a radionetwork node according to some embodiments.

FIG. 17A is a logic flow diagram of a method performed by a network nodeaccording to some embodiments.

FIG. 17B is a logic flow diagram of a method performed by a wirelesscommunication device according to some embodiments.

FIG. 18A is a logic flow diagram of a method performed by a wirelesscommunication device according to other embodiments.

FIG. 18B is a logic flow diagram of a method performed by a radionetwork node according to other embodiments.

FIG. 19A is a logic flow diagram of a method performed by a network nodeaccording to other embodiments.

FIG. 19B is a logic flow diagram of a method performed by a wirelesscommunication device according to other embodiments.

FIG. 20A is a block diagram of a user equipment according to someembodiments.

FIG. 20B is a block diagram of a user equipment according to otherembodiments.

FIG. 20C is a block diagram of a user equipment according to yet otherembodiments.

FIG. 21A is a block diagram of a base station according to someembodiments.

FIG. 21B is a block diagram of a base station according to otherembodiments.

FIG. 21C is a block diagram of a base station according to yet otherembodiments.

FIG. 22A is a block diagram of a network node according to someembodiments.

FIG. 22B is a block diagram of a network node according to otherembodiments.

FIG. 23A is a logic flow diagram of a method performed by a wirelesscommunication device according to still other embodiments.

FIG. 23B is a logic flow diagram of a method performed by a radionetwork node according to still other embodiments.

FIG. 24A is a logic flow diagram of a method performed by a network nodeaccording to still other embodiments.

FIG. 24B is a logic flow diagram of a method performed by a wirelesscommunication device according to still other embodiments.

DETAILED DESCRIPTION

FIG. 1 illustrates a wireless communication system 10 (e.g., anarrowband IoT, NB-IoT, system) according to one or more embodiments.The system 10 includes a radio network node 12 (e.g., an eNB) and awireless communication device 14 (e.g., a user equipment, which may be aNB-IoT device). The device 14 is configured to perform random access,e.g., for initial access when establishing a radio link, fortransmitting a scheduling request, and/or for achieving uplinksynchronization. Regardless of the particular objective achieved by thisrandom access, the device 14 generates a random access preamble signal16 to transmit to the radio network node 12 as part of random access.Where the system 10 is a NB-IoT system, for instance, the device 14 maytransmit the random access preamble signal over a narrowband physicalrandom access channel (NB-PRACH).

The device 14 in this regard generates a random access preamble signal16 that comprises multiple symbol groups 18 (e.g., L number of groups).These multiple symbol groups 18 are shown for example as groups 18A, 18B. . . 18X, 18Y. Each symbol group 18 comprises one or more symbols(e.g., a cyclic prefix and a sequence of five identical symbols).Moreover, the device 14 generates the random access preamble signal 16so that each symbol group 18 occurs during a different time resource(e.g., symbol group interval, such as an OFDM or SC-FDMA symbolinterval). FIG. 1 shows that the device 14 may generate the randomaccess signal 16 in this way by concatenating the multiple symbol groups18 in time, e.g., in a serial or consecutive fashion without overlap.

The device 14 generates the random access preamble signal 16 with eachgroup 18 on a single tone (e.g., a subcarrier, such as an OFDM orSC-FDMA subcarrier). That is, each group 18 during any given timeresource spans only a single tone in frequency. The groups 18 howeverare not all on the same tone. Instead, the device 14 generates therandom access preamble signal 16 according to a frequency hoppingpattern that hops the random access preamble signal transmission fromtone to tone. That is, the frequency hopping pattern governs on whichsingle tone each symbol group 18 will occur on, during its respectivetime resource, so as to effectively hop the single tone on which thesymbol groups 18 occur on in frequency.

Note though that in at least some embodiments the frequency hoppingpattern governs on which single tone symbol groups 18 after the firstsymbol group will occur on. In one embodiment, for instance, the singletone on which the first symbol group occurs is randomly selected (e.g.,from those tones in the signal's transmission bandwidth), and the singletones on which subsequent ones of the symbol groups respectively occuris selected according to (i.e., governed by) the frequency hoppingpattern.

Notably, the frequency hopping pattern hops the random access preamblesignal 16 a fixed frequency distance at one or more symbol groups 18 andhops the random access preamble signal 16 one of multiple differentpossible frequency distances at one or more other symbol groups 18. Thepattern may for instance hop the signal from one of the symbol groups toan adjacent symbol group over a fixed frequency distance, and hop thesignal from another of the symbol groups to an adjacent symbol groupover a pseudo random frequency distance. With each symbol group 18occurring on a single tone during a respective time resource, thefrequency hopping pattern may also be characterized as hopping therandom access preamble signal 16 a fixed frequency distance at one ormore time resources and hopping the random access preamble signal 16 oneof multiple different possible frequency distances at one or more othertime resources.

As shown in FIG. 1, for example, at symbol group 18B (or its respectivetime resource), the pattern hops the random access preamble signal 16 afixed frequency distance D1, such that the symbol group 18B occurs on asingle tone that is a fixed frequency distance D1 away from the singletone on which the previous symbol group 18A occurred. This fixedfrequency distance D1 is illustrated as the frequency distance of asingle tone, since the previous symbol group 18A occurred on an adjacenttone. By contrast, at symbol group 18Y (or its respective timeresource), the pattern hops the random access preamble signal 16 one ofmultiple different possible frequency distances 20 (which may forinstance be pseudo randomly generated or selected), such that the symbolgroup 18Y occurs on a single tone that is one of multiple differentpossible frequency distances 20 away from the single tone on which theprevious symbol group 18X occurred. In some embodiments, therefore, thepattern hops the random access preamble signal 16 at some symbol groupsby a fixed distance, but hops the random access preamble signal 16 atother symbol groups by a variable or pseudo random distance. In anyevent, FIG. 1 shows these possible distances 20 as including frequencydistances D2, D3, and D4, although other examples with two or morepossible distances 20 are of contemplated. Regardless, FIG. 1illustrates as an example that the hopping pattern hops the randomaccess preamble signal 16 a frequency distance D2 at symbol group 18Y(relative to the single tone on which symbol group 18X occurred). Thisfrequency distance D2 may differ from frequency distance D1, especiallyif the multiple different possible frequency distances 20 do not includedistance D1. In this case, therefore, the pattern hops the random accesspreamble signal 16 different frequency distances D1, D2 at differentsymbol groups 18B, 18Y.

In one or more embodiments, as alluded to above, the multiple differentpossible frequency distances 20 include those frequency distances 20which may be pseudo randomly selected or generated, e.g., according to adefined rule or formula. In this case, then, the frequency hoppingpattern hops the random access preamble signal 16 a fixed frequencydistance at one or more symbol groups 18 and hops the random accesspreamble signal 16 a pseudo random frequency distance at one or moreother symbol groups 18. The pattern may for instance hop the randomaccess preamble signal 16 from one of the symbol groups to an adjacentsymbol group over a fixed frequency distance, and hop the random accesspreamble signal 16 from another of the symbol groups to an adjacentsymbol group over a pseudo random frequency distance. Accordingly,frequency distance D1 in FIG. 1 may be a fixed frequency distancewhereas frequency distance D2 may be a pseudo random frequency distance.

In at least some embodiments, the fixed frequency distance D1 is lessthan or equal to a frequency distance threshold associated with acertain objective. At least one of the multiple different possiblefrequency distances 20 is greater than this frequency distancethreshold. Where the multiple different possible frequency distances 20are pseudo random frequency distances, for instance, this means therange of frequency distances which may be pseudo randomly selected orgenerated includes at least one frequency distance greater than thefrequency distance threshold. This frequency distance threshold may befor instance the distance spanned by one or two tones.

In some embodiments, for example, this objective is a targeted cell sizeand/or a targeted time-of-arrival estimation range, e.g., for uplinksynchronization purposes. In this case, the frequency distance thresholdmay be set to not only achieve this objective, but also to achieve atarget timing estimation accuracy.

More particularly in this regard, the phase difference of two adjacentreceived symbol groups caused by hopping is prone to a 2*Pi phaseambiguity, which may cause confusion in the time-of-arrival estimation.A large hopping distance D may be chosen in an effort to avoid the 2*Piphase ambiguity. But this would come at the cost of reducing thetime-of-arrival estimation range, and in turn reducing the cell sizethat can be supported. Therefore, a small frequency hopping distance maybe used to ensure a certain cell size can be supported. For example,with 35 km cell size and 3.75 kHz subcarrier spacing, there should besome hopping by at most one tone.

On the other hand, the phase difference of two adjacent received symbolgroups due to hopping is proportional to the hopping distance D. Thismeans that choosing a large hopping distance D makes the observed phasedifference more robust to noise, which in turn helps improvetime-of-arrival estimation performance. Effectively, then, timingestimation accuracy is inversely proportional to the signal bandwidth ortransmission bandwidth of the random access preamble signal 14. That is,spreading the signal over a wider bandwidth achieves better timingestimation accuracy. This means that, when pseudo random hopping isused, the wider the pseudo random hopping range, the narrower thecorrelation peak for time-of-arrival estimation, and thus the moreaccurate the estimation.

Achievement of both a target time-of-arrival estimation range and atarget timing estimation accuracy is therefore accomplished in someembodiments by employing a frequency hopping pattern that sometimes hopswith a frequency distance which is small enough to achieve a targetedestimation range and that at other times hops with a frequency distancewhich is large enough to achieve a targeted estimation accuracy. Inother words, multiple frequency distances (i.e., multiple levels orsizes) for frequency hopping are used (e.g., additional hopping is usedon top of the first level fixed size hopping). Multiple frequencydistances are used, though, with the constraint that there should besome hopping distances small enough to allow sufficient time-of-arrivalestimation range (equivalently, to support a target cell size).

Alternatively or additionally, the frequency hopping pattern in FIG. 1hops the random access preamble signal 16 a fixed frequency distance ateach symbol group in a first set of one or more symbol groups, and hopsthe random access preamble signal 16 one of multiple different possiblefrequency distances at each symbol group in a second set of one or moresymbol groups different than the first set. The first and second sets inthis regard may be interlaced in time and non-overlapping, with bothsets including every other symbol group. The multiple different possiblefrequency distances may be for instance pseudo-randomly generated orselected. Regardless, the fixed frequency distance may be set to achievea defined objective as described above (e.g., required a small frequencydistance), whereas the multiple different possible frequency distancesmay be established to hop the random access preamble signal 16 acrossall or substantially all of the signal bandwidth (e.g., to improvetiming estimation accuracy).

In these or other embodiments, the frequency hopping pattern may begenerated as a combination of two hopping patterns; namely, a fixeddistance hopping pattern and a multi-distance hopping pattern. The fixeddistance hopping pattern hops the random access preamble signal 16 afixed frequency distance at each symbol group in a first set of one ormore symbol groups. The multi-distance hopping pattern hops the randomaccess preamble signal 16 one of multiple different possible frequencydistances at each symbol group in a second set of one or more symbolgroups different than the first set. This multi-distance hopping patternmay be a pseudo-random hopping pattern.

FIG. 2 illustrates one example where a frequency distance hopped at asymbol group in the second set is selected from candidate frequencydistances that include 0, 1, . . . and N_(b) ^(sc)−1 multiples of afrequency distance spanned by a single tone, where N_(b) ^(sc) is anumber of tones in a transmission bandwidth of the random accesspreamble signal and/or a number of tones within which hopping is definedfor the random access preamble signal 16. FIG. 2 illustrates thisexample in an LTE or NB-IoT context where the signal is transmitted overa narrowband physical random access channel, NB-PRACH, with N_(b)^(sc)=12. The symbol groups in FIG. 2 are consecutively indexed in timevia an index t. This symbol group index t may be referred to as a PRACHgroup index.

In FIG. 2, at each even PRACH group index t, i.e., 0, 2, 4, . . . , thehopping is pseudo random and can be any value in the PRACH band (i.e.,any value between 0 and 11, with N_(b) ^(sc)=12). At each odd PRACHgroup index t, the hopping is a fixed size hopping (e.g., 1 tone)relative to the tone used at the PRACH group index t−1. Accordingly,every N_(sb) ^(sc)=2n_(micro) tones in a PRACH band may be called aPRACH subband, where n_(micro) denotes the size of the fixed hopping.For example, in FIG. 2, the size of fixed hopping is 1, and every N_(sb)^(sc)=2 tones in the PRACH band constitute a PRACH subband. The PRACHband thereby consists of multiple different subbands, with each subbandbeing a subset of the PRACH band in which the random access preamblesignal is hopped by a fixed frequency distance. In other embodiments notshown where the size of the fixed hopping is 2 tones, every N_(sb)^(sc)=2*2=4 tones in the PRACH band constitute a PRACH subband.Therefore, the number N_(b) ^(sc) of tones in a PRACH band should bedivisible by N_(sb) ^(sc) to fully use all the frequency resources.

At least some embodiments fully utilize the frequency resources forPRACH, by hopping the random access preamble signal 16 across thePRACH's bandwidth, e.g., such that the symbol groups 18 span the PRACH'sbandwidth. According to the embodiment shown in FIG. 2, for instance,the fixed size hopping at a particular odd group index can be either“Upward” or “Downward,” while the hopping at an even index is pseudorandom. For a PRACH transmission located in a PRACH subband, if thetransmission uses a tone in the lower half of the subband at an evengroup index t, the transmission will jump “Upward” at group index t+1.If the transmission uses a tone in the upper half of the subband at aneven group index t, the transmission will jump “Downward” at group indext+1. In this and other embodiments, therefore, the frequency hoppingpattern hops the random access preamble signal 16 the fixed frequencydistance at a symbol group in a direction that depends on a frequencylocation of the symbol group.

FIG. 3 illustrates a different example where instead a frequencydistance hopped at a symbol group in the second set is selected fromcandidate frequency distances that include 0, N_(sb) ^(sc), 2N_(sb)^(sc), . . . , and N_(b) ^(sc)−N_(sb) ^(sc) multiples of a frequencydistance spanned by a single tone, wherein N_(b) ^(sc) is a number oftones in a transmission bandwidth of the random access preamble signal,and wherein N_(sb) ^(sc) is a number of tones in any given subband. FIG.3 again illustrates this example in an LTE or NB-IoT context where thesignal is transmitted over the PRACH, with N_(b) ^(sc)=12 and N_(sb)^(sc)=2.

In FIG. 3, at each even PRACH group index, i.e., 0, 2, 4, . . . , thehopping is pseudo random in a subset of tones in the PRACH band. At eachodd PRACH group index t, the hopping is a fixed size hopping relative tothe tone used at the PRACH group index t−1. The fixed size hopping isalways “Upward” or always “Downward”. In FIG. 3, the size of fixedhopping is 1.

Note the differences of the hopping pattern in FIG. 3 from the hoppingpattern in FIG. 2. The pseudo random hopping pattern in FIG. 3 is PRACHsubband based, while the pseudo random hopping in FIG. 1 is tone based.In other words, the possible sizes of pseudo random hopping in FIG. 2can be 0, 1, 2, . . . , N_(b) ^(sc)−1, while the possible sizes ofpseudo random hopping in FIG. 3 can only be 0, N_(sb) ^(sc), 2N_(sb)^(sc), . . . , N_(sb) ^(sc). Again it is assumed that number N_(b) ^(sc)of tones in a PRACH band is divisible by N_(sb) ^(sc). Further, for aparticular PRACH transmission, with the hopping pattern illustrated inFIG. 3 the fixed size hopping is always either “Upward” or “Downward”during the transmission, while the hopping pattern illustrated in FIG. 2the fixed size hopping may change between “Upward” and “Downward.” Thesedifferences can be seen in FIGS. 2 and 3.

Since each PRACH preamble effectively only uses one tone during anygiven time resource, different preambles can be multiplexed in thefrequency domain. In some embodiments, therefore, the radio network node12 is configured to receive one or more other signals from one or moreother user equipments, and process those one or more other signals in anattempt to detect one or more other random access preamble signalsmultiplexed in frequency with the random access preamble signal 16,according to different frequency hopping patterns.

The hopping patterns are designed in some embodiments such that thefrequency resources can be fully utilized by PRACH. For example, FIG. 4shows the multiplexing of 12 PRACH frequency hopping patterns,corresponding to the hopping pattern illustrated in FIG. 2. Each fillpattern (or reference number/letter) represents one frequency hoppingpattern. FIG. 5 shows the multiplexing of 12 PRACH frequency hoppingpatterns, corresponding to the hopping pattern illustrated in FIG. 3. Ingeneral, N tones can be configured for multiplexing N PRACH frequencyhopping patterns. Each PRACH hopping pattern uses one tone during oneOFDM symbol group interval, and the hopping patterns according toembodiments herein (as shown in FIGS. 4 and 5) ensure no two hoppingpatterns use the same tone during the same OFDM symbol group interval.

According to some embodiments, the detailed formulas for the hoppingpattern illustrated in FIGS. 2 and 4 are given as follows.

$\mspace{20mu} {{{(t)} = {n_{start} + {\left( {n_{sc} + {f_{hop}(i)}} \right){{mod}N}_{b}^{sc}}}},{i = \frac{t}{2}},{t = 0},2,4,\cdots}$$\mspace{79mu} {{(t)} = {{\left( {t - 1} \right)} + {\left( {1 - {2 \star \left\lfloor \frac{\left( {t - 1} \right){{mod}\left( {2n_{micro}} \right)}}{n_{micro}} \right\rfloor}} \right) \star {\quad{n_{micro},\mspace{79mu} {t = 1},3,5,{{\ldots {f_{hop}(i)}} = {\left( {{f_{hop}\left( {i - 1} \right)} + {\left( {\sum\limits_{k = {{i \star 10} + 1}}^{{i \star 10} + 9}{{c(k)} \star 2^{k - {({{i \star 10} + 1})}}}} \right){{mod}\left( {N_{b}^{sc} - 1} \right)}} + 1} \right){{mod}N}_{b}^{sc}}}}}}}}$

Here, n_(start) denotes the starting index of the PRACH band, n—is therelative tone index in the PRACH band (relative to n_(start)), n_(micro)is the size of the fixed hopping, N_(b) ^(sc) is the number of tones ina transmission bandwidth of the random access preamble signal,f_(hop)(−1)=0. An example of the pseudo-random sequence c(k) can be theone given by clause 7.2 in 3GPP TS 36.211 v13.0.0. In particular, thepseudo random sequence c(k) comprises a sequence of length M_(PN), wherek=0, 1, . . . , M_(PN)−1, and is defined by

c(k)=(x ₁(k+N _(C))+x ₂(k+N _(C))mod 2

x ₁(k+31)=(x ₁(k+3)+(k))mod 2

x ₂(k+31)=(x ₂(k+3)+x ₂(k+2)+x ₂(k+1)+x ₂(k))mod 2

where N_(C)=1600, x₁(0)=1, x₁(k)=0, k=1, 2, . . . , 30, c_(init)=Σ_(i=0)³⁰x₂(i)·2^(i), and c_(init)=N_(ID) ^(Ncell) if cell-specific hopping isdesired. N_(ID) ^(cell) is a physical-layer cell identity.

As this example demonstrates, therefore, the pseudo-random sequencegenerator can be cell specific if needed. For example, the pseudo-randomsequence c(k) given by clause 7.2 in 36.211 can be initialized with cellID if desired.

In this and other embodiments where hopping is cell specific, pseudorandom hopping may be viewed as a type of cell specific code divisionmultiplexing (CDM). This CDM allows neighboring cells to use the samefrequency resources for NB-PRACH. This in turn greatly increasesNB-PRACH capacity, compared to FDM of NB-PRACH among neighboring cells.Specifically, with 180 kHz bandwidth and 3.75 kHz subcarrier spacing, upto 48 NB-PRACH preambles can be used in a cell.

The detailed formulas for the hopping pattern illustrated in FIGS. 3 and5 are given as follows.

$\mspace{79mu} {{{(t)} = {n_{start} + {\left( {n_{sc} + {{f_{hop}(i)} \star \frac{N_{b}^{sc}}{2n_{micro}}}} \right){{mod}N}_{b}^{sc}}}},{i = \frac{t}{2}},\mspace{79mu} {t = 0},2,4,\cdots}$$\mspace{79mu} {{(t)} = {{\left( {t - 1} \right)} + {\left( {1 - {2 \star \left\lfloor \frac{n_{sc}{{mod}\left( {2n_{micro}} \right)}}{n_{micro}} \right\rfloor}} \right) \star {\quad{n_{micro},\mspace{79mu} {t = 1},3,5,{{\ldots {f_{hop}(i)}} = {\quad\left( {{f_{hop}\left( {i - 1} \right)} + {\left( {\sum\limits_{k = {{i \star 10} + 1}}^{{i \star 10} + 9}{{c(k)} \star 2^{k - {({{i \star 10} + 1})}}}} \right){{mod}\left( {\frac{N_{b}^{sc}}{2n_{micro}} - 1} \right)}} + {\left. \quad 1 \right){mod}\frac{N_{b}^{sc}}{2n_{micro}}}} \right.}}}}}}}$

Here n_(start) denotes the starting index of the PRACH band, n_(sc) isthe relative tone index in the PRACH band (relative to n_(start)),n_(micro) is the size of the fixed hopping N_(b) ^(sc) is the number oftones in a transmission bandwidth of the random access preamble signal,f_(hop)(−1)=0. An example of the pseudo-random sequence c(k) can be theone given by clause 7.2 in 36.211 v13.0.0, as detailed above. And,again, the pseudo-random sequence generator can be cell specific ifneeded. For example, the pseudo-random sequence c(k) given by clause 7.2in 36.211 can be initialized with cell ID if desired.

Note that the above are just two examples of possible hopping patterns.Any hopping patterns that use both fixed size hopping and additionalmulti-level hopping may be employed by certain embodiments herein. Themulti-level hopping constitutes any hopping where the size hopped at anygiven symbol group (or time resource) is one of multiple differentfrequency distances defined as possible for that hopping. Multi-levelhopping can be achieved by (but not limited to), for example, pseudorandom hopping, as illustrated in the above examples. Specifically, thepseudo random hopping may be equivalently considered as hopping wherethe size hopped at any given symbol group (or time resource) may be oneof multiple predetermined hopping sizes (which are determined in advanceby specified pseudo random formulas). The fixed size hopping includesboth “Upward” and “Downward” hopping to fully utilize frequencyresource. The fixed size hopping ensures the targeting time-of-arrivalestimation range can be met by PRACH. The additional multi-level hopping(achieved for example via pseudo random hopping) greatly improves thetime-of-arrival estimation accuracy.

Indeed, FIG. 6 shows that the hopping patterns according to someembodiments can help the base station obtain very accurate time ofarrival estimation accuracy even if the preamble transmission only usesone single tone of 3.75 kHz at a time. FIG. 6 in this regard shows thisfor PRACH bands that include different numbers of tones, including an8-tone PRACH band 22, a 12-tone PRACH band 24, and a 16-tone PRACH band26.

In some embodiments, each base station configures one or more PRACHbands, e.g., for different types of user equipments. The number of tonesin each band can be different. For example, if frequency divisionmultiplexing of PRACH transmissions of different coverage classes isallowed, a base station may configure PRACH bands of differentbandwidths for different coverage classes. A larger band may be used forlonger preambles. The PRACH bands of neighboring cells may or may notoverlap. In case of overlapping, cell-specific pseudo random hopping maybe used to distinguish preambles in neighboring cells and/or to mitigateinter-cell interference. Each band may for instance be characterized bya starting tone index n_(start), and the number of tones in thetransmission bandwidth of the random access preamble signal N_(b) ^(sc)(or the ending tone index). Each band may also be characterized by thesize of the fixed hopping n_(micro).

In any event, an illustration of a possible NB-PRACH configuration of abase station is given in FIG. 7. As shown, the base station configures afirst NB-PRACH band 1 which includes X number of tones, a secondNB-PRACH band 2 which includes Y number of tones, and a third NB-PRACHband 3 which includes Z number of tones. These three bands are allconfigured within the 180 kHz bandwidth of a narrowband carrier (e.g., 1physical resource block).

For contention based random access with one or more NB-PRACH bandsconfigured, the device 14 in some embodiments first randomly selects atone in the configured PRACH frequency resource pool that may includeone or more PRACH bands. The device 14 may for instance randomly selecta single tone from among the tones included in the one or more PRACHbands configured. The device 14 then transmits the random accesspreamble signal 16 in the corresponding PRACH band according to afrequency hopping pattern as described above.

The hopping patterns herein are general and apply to any subcarrierspacing, any preamble length (i.e., number of symbol groups), any sizeof fixed hopping, and any number of tones in a PRACH band. FIG. 8provides another example of a hopping pattern with an 8-tone PRACH bandand 2-tone fixed hopping. The hopping pattern is generated in the sameway as FIG. 4. FIG. 9 provides another example of the hopping patternwith 8-tone PRACH band and 2-tone fixed hopping. The hopping pattern isgenerated in the same way as FIG. 5.

According to one or more embodiments, one or more of the configurationparameters of PRACH such as the starting index of the PRACH band(n_(start)), the number of tones in the PRACH band (N_(b) ^(sc)), andthe size of the fixed hopping (n_(micro)), are signaled as configurationinformation, e.g., using a System Information Block (SIB), or a MasterInformation Block (MIB), or the combination of MIB and SIB. Note thatsome of these configurations may be fixed and thus does not need to besignaled.

Note that while the description above focuses on orthogonal resourceallocation in frequency domain with frequency hopping, it is understoodby those skilled in the art that resource allocation in other dimensionis also possible. For example, in the time domain, non-overlapping setsof subframes can be used to define orthogonal PRACH resources; in thesequence domain, orthogonal preamble sequences can be used by differentUEs even when their time/frequency resources overlap. It is understoodthat configuration parameters defining time-domain aspects andsequence-domain aspects are also defined, either in a fixed manner orbroadcast via MIB and/or SIB. Frequency domain configuration herein isto be used together with those of time and sequence domain to fullydefine the PRACH resource configuration.

As noted above, random access embodiments herein may be applied toLTE-based systems and/or NB-IoT systems. In this context, with respectto the existing LTE random access design, random access serves multiplepurposes such as initial access when establishing a radio link,scheduling request, etc. Among others, a main objective of random accessis to achieve uplink synchronization, which is important for maintainingthe uplink orthogonality in LTE. To preserve orthogonality amongdifferent user equipments (UE) in an OFDMA or SC-FDMA system, the timeof arrival of each UE's signal needs to be within the cyclic prefix (CP)of the OFDMA or SC-FDMA signal at the base station.

LTE random access can be either contention-based or contention-free. Thecontention-based random access procedure consists of four steps, asillustrated in FIG. 10. Note that only the first step involvesphysical-layer processing specifically designed for random access, whilethe remaining three steps follow the same physical-layer processing usedin uplink and downlink data transmission. For contention-free randomaccess, the UE uses reserved preambles assigned by the base station. Inthis case, contention resolution is not needed, and thus only Steps 1and 2 are required.

As shown in FIG. 10, in the first step, a random access preamble signal16 is sent by the UE in the form of a random access preamble 28 over aphysical random access channel (PRACH). This preamble 28 may also bereferred to as a PRACH preamble, a PRACH preamble sequence, or a PRACHsignal. Regardless, the UE transmits the random access preamble 28during a random access time segment illustrated in FIG. 11. The randomaccess preamble 28 does not occupy the entire random access segment,leaving some time as guard time 30. As discussed earlier, to maximize PAefficiency and coverage, it is desirable to have PRACH preambles asclose to constant-envelope as possible. Also, the PRACH preambles shouldbe designed such that accurate time-of-arrival estimation can beperformed by the base stations.

The basic structure of a PRACH symbol group (e.g., a symbol group 18)according to some embodiments herein is illustrated in FIG. 12, and anexample is given in FIG. 13. It is basically a single tone (subcarrier)OFDM signal. Unlike a traditional OFDM symbol where thenon-cyclic-prefix (non-CP) part consists of a single symbol, the non-CPpart of the PRACH symbol group may consist of one or more symbols.

The symbols in the random access preamble signal 16 can be allidentical, even across different symbol groups. In this case, it may beeasier to guarantee phase continuity between adjacent symbol groups andthus help maintain close-to-zero peak-to-average-power ratio (PAPR) ofthe preamble signal. In other embodiments, by contrast, the symbols in agroup are identical, but may be different across symbol groups. This maybe viewed as applying an additional layer of code division multiplexing(CDM) over groups. In this case it is not easier to guarantee phasecontinuity between adjacent symbol groups, but the embodiment furtherrandomizes the interference to other transmissions from a system levelperspective.

In yet other embodiments, the symbols in a group are different, but thewhole symbol group is repeated across groups. This may be seen asapplying an additional layer of CDM within a group. In this case it isnot easier to guarantee phase continuity between adjacent symbol groups,but the embodiment further randomizes the interference to othertransmissions from a system level perspective, albeit in a limited sensebecause symbols only change within a group.

In still other embodiments, symbols can be different both within a groupand across groups. This may be seen as applying an additional layer ofCDM over symbols, such that CDM is applied to each symbol group so as tomake symbols in a group possibly different. In this case it is noteasier to guarantee phase continuity between adjacent symbol groups, butthe embodiment randomizes the interference to other transmissions from asystem level perspective to the greatest possible extent.

In a further embodiment, the last symbol in each symbol group is fixed.Since the cyclic prefix is the same as a last part of the whole of thelast symbol, this structure makes it easier to guarantee phasecontinuity between adjacent symbol groups and thus helps maintainclose-to-zero PAPR of the preamble signal. If additional interferencerandomization (in addition to those brought by pseudo random hopping,logical tone index, and/or cell ID dependent sequence values) isdesired, values for other symbols may be appropriately chosen.

The specific values of the symbol(s) in a group, whether they are allidentical or different, may in some embodiments be cell ID dependentand/or logical tone index dependent.

According to the example in FIG. 13, the subcarrier spacing is 3.75 kHz.However, embodiments herein apply to any subcarrier spacing. Accordingto some embodiments, the PRACH signal consisting of one or more symbolgroups is spread in time. Thus, a number of OFDM symbol groups, each oneas illustrated in FIG. 12, are concatenated to form a PRACH preamble.That is, each group 18 as described above may comprise that illustratedin FIGS. 12 and/or 13. But the frequency positions of the symbol groups18 of the same PRACH preamble vary according to a hopping pattern asdescribed above.

As suggested above, a tone as used herein may correspond to a subcarrierin some embodiments. A tone may for instance correspond to an OFDMsubcarrier or an SC-FDMA subcarrier.

Some embodiments herein find particular applicability to NB-IoT. Forexample, to support a 35 km cell size, the fixed size hopping distancemay be limited to 1 tone. And using additional hopping sizes may improvetime-of-arrival estimation accuracy. For example, an additional 6-tonehopping on top of the one-tone hopping may be used. However, the valuesof the second hopping affect the time-of-arrival estimation accuracy.For example, with increased tone hopping value 2, the center of CDF isimproved but the tail is also elevated. The last problem can be solvedif an optimized hopping pattern is used, as detailed in the following.

As opposed to using additional fixed size hopping on top of the one-tonehopping, it may be more beneficial and flexible to use pseudo randomhopping on top of fixed size hopping. Logically, pseudo random hoppingmay be thought of as a type of cell specific CDM if the hopping is cellspecific. The benefits of using pseudo random hopping on top of fixedsize hopping for NB-PRACH are summarized as follows.

First, pseudo random hopping can solve the elevated tail issues and hasthe potential of providing more accurate time-of-arrival estimationaccuracy. In particular, timing estimation accuracy is inverselyproportional to the signal bandwidth. However, with increased tonehopping value 2, the center of CDF is improved but the tail is alsoelevated. This seems to contradict the conventional intuition. Uponfurther consideration, though, the phenomenon is due to the fixedhopping value in the second level. This issue can be solved by pseudorandom hopping, as shown in FIG. 14A-D.

Specifically, due to 2*Pi phase rotation ambiguity, hopping by more thanone tone can introduce side peaks with 35 km cell size. The larger thesecond level hopping value, the more the side peaks, as shown in FIGS.14A and 14B. These side peaks cause estimation errors and lead to theelevated error tails. In contrast, pseudo random hopping solves thisissue, as shown in FIGS. 14C and 14D. Further, the wider the pseudorandom hopping range, the narrower the correlation peak (and thuspotentially the more accurate the estimation would be). This matches theconventional wisdom that a signal of wider bandwidth can enable bettertiming estimation performance.

Second, pseudo random hopping is already implemented in LTE for otherpurposes. Pseudo random hopping according to some embodiments herein isreused for NB-IoT. For NB-PRACH, a pseudo random hopping similar to LTEPUSCH type 2 hopping (see TS 36.211 (Release 12) and TS 36.213 (Release12) can be used on top of the fixed size (e.g., one tone) hopping.

Third, pseudo random hopping can mitigate inter-cell interference.Without pseudo random hopping, the NB-PRACH transmissions in one cellmay cause persistent interference to the NB-PRACH and/or NB-PUSCHtransmissions in the neighboring cells. Persistent interference mayexist even in the same cell, because (i) multiple intra-cell NB-PRACHtransmissions at the same time may not be fully orthogonal due to e.g.residual carrier frequency offsets, and (ii) NB-PUSCH and NB-PRACH arenot orthogonal if they are frequency multiplexed.

Fourth, pseudo random hopping may increase NB-PRACH capacity.Neighboring cells may configure different frequency resources forNB-PRACH. While this approach avoids inter-cell NB-PRACH interference,this may reduce NB-PRACH capacity. In particular, there may only be 12tones (or equivalently, 12 preambles) in a cell. Note that each cell mayreserve some preambles for contention free random access. Also, if LTEtype preamble partition was used to indicate information in Msg1, thenumber of available preambles would become even more limited in eachpartitioned group. Putting these together, NB-PRACH may become thebottleneck of the NB-IoT system if its resource is not carefullydimensioned.

As mentioned earlier, pseudo random hopping may be thought of as a typeof cell-specific CDM. This CDM allows neighboring cells to use the samefrequency resources for NB-PRACH. This greatly increases NB-PRACHcapacity, compared to FDM of NB-PRACH among neighboring cells.Specifically, with 180 kHz bandwidth and 3.75 kHz subcarrier spacing, upto 48 NB-PRACH preambles can be used in a cell.

Fifth, pseudo random hopping provides more hopping flexibility and ismore forward compatible. Indeed, two-level hopping with two fixedhopping sizes may impose some restriction on possible NB-PRACH resourceconfiguration. In particular, two-level hopping always requires theNB-PRACH band to have 12 tones, which is not flexible.

In contrast to two-level hopping with two fixed hopping sizes, pseudorandom hopping essentially uses multiple hopping sizes and is moreflexible. For example, a cell may configure different NB-PRACHbandwidths. NB-PRACH transmission with one-level fixed hopping plusadditional pseudo random hopping can be readily scaled as the bandwidthincreases. If fixed-size two-level hopping is used, many differenthopping sizes may need to be defined.

Moreover, frequency hopping will likely become a NB-IoT feature infuture especially when multiple NB-IoT PRBs are configured. Using pseudorandom hopping is more forward compatible. If fixed-size two-levelhopping is used, additional hopping sizes might need to be defined infuture when more NB-IoT PRBs are available.

In some embodiments, the preamble length should be long enough to helpthe base station accumulate enough energy to obtain satisfactoryperformance, including for instance high detection rate, low false alarmrate, and good timing estimation accuracy. Therefore, depending on thecoverage target, the preamble length may be chosen accordingly. Multiplelengths in this regard may be defined if the single tone frequencyhopping PRACH is used for all coverage classes.

Note that in embodiments which employ pseudo random hopping, the pseudorandom hopping range may be related to the preamble length to someextent. In particular, if a preamble length is short, but the pseudorandom hopping range is large, many correlation side peaks may arise.This is illustrated in FIGS. 15A-15F. Indeed, as shown in FIGS. 15A-15C,shorter preambles for users with 144 dB MCL results in more substantialcorrelation side peaks for larger pseudo random hopping ranges. Bycontrast, as shown in FIGS. 15D-15F, longer preambles for users with 164dB MCL results in less substantial correlation side peaks than those inFIGS. 15A-15C, even for the same pseudo random hopping ranges. Thismeans that longer preamble lengths can afford larger pseudo randomhopping ranges. Accordingly, in some embodiments, different pseudorandom hopping ranges are used for different preamble lengths (e.g.,large range for long preamble length and short range for short preamblelength).

In some embodiments, the eNB may be able to configured the followingparameters of single tone frequency hopping NB-PRACH: time resourceinformation that informs UEs “when to send”, preamble sequenceinformation that directs UEs “what to send”, and frequency resourceinformation that directs UEs “where to send”. Therefore, in someembodiments, NB-IoT UEs may have the following knowledge to send asingle tone frequency hopping NB-PRACH preamble: possible starting timesof NB-PRACH possibilities, preamble sequence values, starting indices ofone or more NB-PRACH bands, CP length, number of symbols per group,number of groups, micro hopping size, and/or pseudo random hoppingrange. This information may be signaled using a System Information Block(SIB) or a Master Information Block (MIB), or a combination of SIB andMIB. Some of these configurations may be fixed and thus do not need tobe signaled.

As an example, a set of design configuration parameters may besummarized in Table 1 below:

Number Pseudo Cell Subcarrier of Number random size MCL spacing Tcpsymbols of Hopping hopping (km) (dB) (kHz) (us) per group groups patternrange 35 144 3.75 266.7 5 8 1 tone micro {8, 12, 16} hopping + tonespseudo random hopping 154 3.75 266.7 5 24 1 tone micro {8, 12, 16}hopping + tones pseudo random hopping 164 3.75 266.7 5 120 1 tone micro{8, 12, 16} hopping + tones pseudo random hopping 8 144 3.75 66.7 5 8 {1or 4} tone {8, 12, 16} micro hopping + tones pseudo random See Remarkhopping 1 154 3.75 66.7 5 24 {1 or 4} tone {8, 12, 16} micro hopping +tones pseudo random hopping 164 3.75 66.7 5 120 {1 or 4} tone {8, 12,16} micro hopping + tones pseudo random hopping Remark 1: The possiblepseudo random hopping ranges are related to the size of the used microhopping.

Despite particular applicability to NB-IoT in some examples, though, itwill be appreciated that the techniques may be applied to other wirelessnetworks, including eMTC as well as to successors of the E-UTRAN. Thus,references herein to signals using terminology from the 3GPP standardsfor LTE should be understood to apply more generally to signals havingsimilar characteristics and/or purposes, in other networks.

A radio node herein is any type of node (e.g., a base station orwireless communication device) capable of communicating with anothernode over radio signals. A radio network node 12 is any type of radionode capable and/or configured to operate within a wirelesscommunication network, such as a base station. A network node is anytype of node capable and/or configured to operate within a wirelesscommunication network, whether within a radio access network or a corenetwork of the wireless communication network. A wireless communicationdevice 14 is any type of radio node capable of communicating with aradio network node over radio signals. A wireless communication device14 may therefore refer to a machine-to-machine (M2M) device, amachine-type communications (MTC) device, a NB-IoT device, etc. Awireless communication device may also be referred to as a userequipment, a radio device, a radio communication device, a wirelessterminal, or simply a terminal—unless the context indicates otherwise,the use of any of these terms is intended to include device-to-deviceUEs or devices, machine-type devices or devices capable ofmachine-to-machine communication, sensors equipped with a wirelesscommunication device, wireless-enabled table computers, mobileterminals, smart phones, laptop-embedded equipped (LEE), laptop-mountedequipment (LME), USB dongles, wireless customer-premises equipment(CPE), etc. In the discussion herein, the terms machine-to-machine (M2M)device, machine-type communication (MTC) device, wireless sensor, andsensor may also be used. It should be understood that these devices maybe a UE.

In an IOT scenario, a wireless communication device 14 as describedherein may be, or may be comprised in, a machine or device that performsmonitoring or measurements, and transmits the results of such monitoringmeasurements to another device or a network. Particular examples of suchmachines are power meters, industrial machinery, or home or personalappliances, e.g. refrigerators, televisions, personal wearables such aswatches etc. In other scenarios, a wireless communication device asdescribed herein may be comprised in a vehicle and may performmonitoring and/or reporting of the vehicle's operational status or otherfunctions associated with the vehicle.

Furthermore, in an NB-IoT context, it may be the case that, to supportlower manufacturing costs for NB-IOT devices, the transmission bandwidthis reduced to one physical resource block (PRB) of size 180 KHz. Bothfrequency division duplexing (FDD) and TDD are supported. For FDD (i.e.the transmitter and receiver operate at different carrier frequencies)only half-duplex mode needs to be supported in the UE. The lowercomplexity of the devices (e.g. only one transmission/receiver chain)means that a small number of repetitions might be needed also in normalcoverage. Further, to alleviate UE complexity, the working assumptionmay be to have cross-subframe scheduling. That is, a transmission isfirst scheduled on Enhanced Physical DL Control Channel (E-PDCCH akaM-EPDCCH) and then the first transmission of the actual data on thePhysical DL Shared Channel (PDSCH) is carried out after the finaltransmission of the M-EPDCCH.

One or more embodiments herein thus generally include using a singlesubcarrier signal in any OFDM or SC-FDMA symbol group interval forrandom access. In different OFDM or SC-FDMA symbol intervals differentsubcarrier (frequencies) may be used. This can be thought of as“frequency hopping”. The hopping patterns consist of both fixed sizehopping and additional multi-level hopping. Fixed size hopping includesboth “Upward” and “Downward” hopping to fully utilize frequencyresource. Fixed size hopping ensures the targeting time-of-arrivalestimation range can be met by PRACH. The multi-level hopping sizes canbe achieved by, for example, pseudo random hopping that can beconsidered as hopping of different sizes that is predetermined. Theadditional multi-level hopping greatly improves the time-of-arrivalestimation accuracy. Orthogonal frequency-hopping patterns betweendifferent PRACH preambles may be designed.

Since the new PRACH signal achieves close to 0 dB PAPR, it reduces theneed for PA backoff to the greatest extent and maximizes PA efficiency.Thus, it maximizes the PRACH coverage and battery efficiency. The newPRACH signal is compatible with SC-FDMA and orthogonalfrequency-division multiple-access (OFDMA). Thus, it can be easilyimplemented using existing SC-FDMA or OFDMA signal generator. Thisreduces both development cost and time-to-market. Further, hoppingpatterns are carefully designed such that (1) accurate time-of-arrivalestimation can be performed by the base station, (2) the frequencyresources can be fully utilized by PRACH while maintaining orthogonalityof different preambles. The accurate time-of-arrival estimation isextremely important if a short CP (like 4.7 us in LTE) is used in PUSCHof NB-IoT.

In view of the various modifications and variations described above,those skilled in the art will appreciate that the wireless communicationdevice 14 (e.g., user equipment) herein may perform the processing 100shown in FIG. 16A for transmitting a random access preamble signal. Thisprocessing 100 comprises generating a random access preamble signal thatcomprises multiple symbol groups, with each symbol group on a singletone during a different time resource, according to a frequency hoppingpattern that hops the random access preamble signal a fixed frequencydistance at one or more symbol groups and hops the random accesspreamble signal a pseudo random frequency distance at one or more othersymbol groups (Block 110). Each symbol group comprises one or moresymbols. The processing 100 further entails transmitting the randomaccess preamble signal (Block 120).

Those skilled in the art will also appreciate that the radio networknode 12 may perform the processing 200 shown in FIG. 16B for receiving arandom access preamble signal. The processing 200 comprises receiving asignal from a wireless communication device (e.g., a user equipment)(Block 210). Processing 200 also includes processing the received signalin an attempt to detect a random access preamble signal that comprisesmultiple symbol groups, with each of the symbol groups on a single toneduring a different time resource, according to a frequency hoppingpattern that hops the random access preamble signal a fixed frequencydistance at one or more symbol groups and hops the random accesspreamble signal a pseudo random frequency distance at one or more othersymbol groups (Block 220). Each symbol group comprises one or moresymbols.

Still further, the radio network node 12 may perform the processing 300shown in FIG. 17A for configuring a wireless communication device (e.g.,a user equipment) to transmit a random access preamble signal comprisingmultiple symbol groups, each symbol group comprising one or moresymbols. The processing 300 comprises generating configurationinformation indicating one or more parameters for a frequency hoppingpattern according to which the wireless communication device is togenerate each of the symbol groups on a single tone during a differenttime resource, wherein the frequency hopping pattern hops the randomaccess preamble signal a fixed frequency distance at one or more symbolgroups and hops the random access preamble signal a pseudo randomfrequency distance at one or more other symbol groups (Block 310). Theprocessing 300 also comprises transmitting the configuration informationto the wireless communication device (Block 320).

The wireless communication device 14 may correspondingly perform theprocessing 400 in FIG. 17B. The processing 400 includes receiving theconfiguration information indicating one or more parameters for afrequency hopping pattern according to which the wireless communicationdevice is to generate each of the symbol groups on a single tone duringa different time resource, wherein the frequency hopping pattern hopsthe random access preamble signal a fixed frequency distance at one ormore symbol groups and hops random access preamble signal a pseudorandom frequency distance at one or more other symbol groups (Block410). Processing 400 also includes configuring the device 14 to generatethe random access preamble signal according to the receivedconfiguration information (Block 420).

In still other embodiments, a user equipment 14 (or, more generally, awireless communication device) herein may perform the processing 500shown in FIG. 18A for transmitting a random access preamble signal. Thisprocessing 500 comprises generating a random access preamble signal thatcomprises multiple symbol groups, with each symbol group on a singletone during a different time resource, according to a frequency hoppingpattern that hops the random access preamble signal from at least one ofthe symbol groups to an adjacent symbol group over a fixed frequencydistance and further hops the random access preamble signal from atleast one of the symbols groups to an adjacent symbol group over apseudo random frequency distance (Block 510). Each symbol groupcomprises one or more symbols. The processing 500 further entailstransmitting the random access preamble signal (Block 520).

Those skilled in the art will also appreciate that, in otherembodiments, a base station 12 (or, more generally, a radio networknode) may perform the processing 600 shown in FIG. 18B for receiving arandom access preamble signal. The processing 600 comprises receiving asignal from a user equipment (Block 610). Processing 600 also includesprocessing the received signal in an attempt to detect a random accesspreamble signal that comprises multiple symbol groups, with each of thesymbol groups on a single tone during a different time resource,according to a frequency hopping pattern that hops the random accesspreamble signal from at least one of the symbol groups to an adjacentsymbol group over a fixed frequency distance and further hops the randomaccess preamble signal from at least one of the symbol groups to anadjacent symbol group over a pseudo random frequency distance (Block620). Each symbol group comprises one or more symbols.

In still further embodiments, a base station 12 (or, more generally, aradio network node) may perform the processing 700 shown in FIG. 19A forconfiguring a user equipment to transmit a random access preamble signalcomprising multiple symbol groups, each symbol group comprising one ormore symbols. The processing 700 comprises generating configurationinformation indicating one or more parameters for a frequency hoppingpattern according to which the wireless communication device is togenerate each of the symbol groups on a single tone during a differenttime resource, wherein the frequency hopping pattern hops the randomaccess preamble signal from at least one of the symbol groups to anadjacent symbol group over a fixed frequency distance and further hopsthe random access preamble signal from at least one of the symbol groupsto an adjacent symbol group over a pseudo random frequency distance(Block 710). The processing 700 also comprises transmitting theconfiguration information to the user equipment (Block 720).

The user equipment 14 may correspondingly perform the processing 800 inFIG. 19B in further embodiments. The processing 800 includes receivingthe configuration information indicating one or more parameters for afrequency hopping pattern according to which the user equipment 14 is togenerate each of the symbol groups on a single tone during a differenttime resource, wherein the frequency hopping pattern hops the randomaccess preamble signal from at least one of the symbol groups to anadjacent symbol group over a fixed frequency distance and further hopsthe random access preamble signal from at least one of the symbol groupsto an adjacent symbol group over a pseudo random frequency distance(Block 810). Processing 800 also includes configuring the user equipment14 to generate the random access preamble signal according to thereceived configuration information (Block 820).

Note that the wireless communication device 14 (e.g., user equipment) asdescribed above may perform the processing herein by implementing anyfunctional means or units. In one embodiment, for example, the wirelesscommunication device 14 comprises respective circuits or circuitryconfigured to perform the steps shown in FIGS. 16A, 17A, 18A, and/or19B. The circuits or circuitry in this regard may comprise circuitsdedicated to performing certain functional processing and/or one or moremicroprocessors in conjunction with memory. In embodiments that employmemory, which may comprise one or several types of memory such asread-only memory (ROM), random-access memory, cache memory, flash memorydevices, optical storage devices, etc., the memory stores program codethat, when executed by the one or more processors, carries out thetechniques described herein.

FIG. 20A illustrates additional details of a user equipment 14 (or, moregenerally, a wireless communication device) in accordance with one ormore embodiments. As shown, the user equipment 14 includes processingcircuitry 920 and radio circuitry 910. The radio circuitry 910 isconfigured to transmit via one or more antennas 940. The processingcircuitry 920 is configured to perform processing described above, e.g.,in FIGS. 16A, 17B, 18A and/or 19B, such as by executing instructionsstored in memory 930. The processing circuitry 920 in this regard mayimplement certain functional means or units.

FIG. 20B illustrates a user equipment 14 (or, more generally, a wirelesscommunication device) that according to other embodiments implementsvarious functional means or units, e.g., via the processing circuitry920 in FIG. 20A. As shown, these functional means or units, e.g., forimplementing the method in FIG. 16A, include for instance a generatingmodule or unit 950 for generating a random access preamble signal thatcomprises multiple symbol groups, with each symbol group on a singletone during a different time resource, according to a frequency hoppingpattern that hops the random access preamble signal a fixed frequencydistance at one or more symbol groups and hops the random accesspreamble signal a pseudo random frequency distance at one or more othersymbol groups, wherein each symbol group comprises one or more symbols.The user equipment 14 also includes a transmitting module or unit 960for transmitting the random access preamble signal.

Additional details of the user equipment 14 are shown in relation toFIG. 20C. As shown in 20C, the example user equipment 14 includes anantenna 940, radio circuitry (e.g. radio front-end circuitry) 910,processing circuitry 920, and the user equipment 14 may also include amemory 930. The memory 930 may be separate from the processing circuitry920 or an integral part of processing circuitry 920. Antenna 940 mayinclude one or more antennas or antenna arrays, and is configured tosend and/or receive wireless signals, and is connected to radiocircuitry (e.g. radio front-end circuitry) 910. In certain alternativeembodiments, user equipment 14 may not include antenna 940, and antenna940 may instead be separate from user equipment 14 and be connectable touser equipment 14 through an interface or port.

The radio circuitry (e.g. radio front-end circuitry) 910 may comprisevarious filters and amplifiers, is connected to antenna 940 andprocessing circuitry 920, and is configured to condition signalscommunicated between antenna 940 and processing circuitry 920. Incertain alternative embodiments, user equipment 14 may not include radiocircuitry (e.g. radio front-end circuitry) 910, and processing circuitry920 may instead be connected to antenna 940 without front-end circuitry910.

Processing circuitry 920 may include one or more of radio frequency (RF)transceiver circuitry, baseband processing circuitry, and applicationprocessing circuitry. In some embodiments, the RF transceiver circuitry921, baseband processing circuitry 922, and application processingcircuitry 923 may be on separate chipsets. In alternative embodiments,part or all of the baseband processing circuitry 922 and applicationprocessing circuitry 923 may be combined into one chipset, and the RFtransceiver circuitry 921 may be on a separate chipset. In stillalternative embodiments, part or all of the RF transceiver circuitry 921and baseband processing circuitry 922 may be on the same chipset, andthe application processing circuitry 923 may be on a separate chipset.In yet other alternative embodiments, part or all of the RF transceivercircuitry 921, baseband processing circuitry 922, and applicationprocessing circuitry 923 may be combined in the same chipset. Processingcircuitry 920 may include, for example, one or more central processingunits (CPUs), one or more microprocessors, one or more applicationspecific integrated circuits (ASICs), and/or one or more fieldprogrammable gate arrays (FPGAs).

The user equipment 14 may include a power source 950. The power source950 may be a battery or other power supply circuitry, as well as powermanagement circuitry. The power supply circuitry may receive power froman external source. A battery, other power supply circuitry, and/orpower management circuitry are connected to radio circuitry (e.g. radiofront-end circuitry) 910, processing circuitry 920, and/or memory 930.The power source 950, battery, power supply circuitry, and/or powermanagement circuitry are configured to supply user equipment 14,including processing circuitry 920, with power for performing thefunctionality described herein.

Also note that the radio network node 12 as described above may performthe processing herein by implementing any functional means or units. Inone embodiment, for example, the radio network node 12 comprisesrespective circuits or circuitry configured to perform the steps shownin FIGS. 16B, 17A, 18B, and/or 19A. The circuits or circuitry in thisregard may comprise circuits dedicated to performing certain functionalprocessing and/or one or more microprocessors in conjunction withmemory. In embodiments that employ memory, which may comprise one orseveral types of memory such as read-only memory (ROM), random-accessmemory, cache memory, flash memory devices, optical storage devices,etc., the memory stores program code that, when executed by the one ormore processors, carries out the techniques described herein.

FIG. 21A illustrates additional details of a radio network node 12(e.g., a bas station) in accordance with one or more embodiments. Asshown, the radio network node 12 includes processing circuitry 1020 andradio circuitry 1010. The radio circuitry 1010 is configured to transmitvia one or more antennas 1040. The processing circuitry 1020 isconfigured to perform processing described above, e.g., in FIGS. 16B,17A, 18B, and/or 19A, such as by executing instructions stored in memory1030. The processing circuitry 1020 in this regard may implement certainfunctional means or units.

FIG. 21B illustrates a radio network node 12 (e.g., a base station) thataccording to other embodiments implements various functional means orunits, e.g., via the processing circuitry 1020 in FIG. 21A. Thesefunctional means or units, e.g., for implementing the method in FIG.16B, include for instance a receiving module or unit 1050 for receivinga signal from a user equipment. Further included is a processing moduleor unit 1060 for processing the received signal in an attempt to detecta random access preamble signal that comprises multiple symbol groups,with each of the symbol groups on a single tone during a different timeresource, according to a frequency hopping pattern that hops the randomaccess preamble signal a fixed frequency distance at one or more symbolgroups and hops the random access preamble signal a pseudo randomfrequency distance at one or more other symbol groups, wherein eachsymbol group comprises one or more symbols.

Additional details of the radio network node 12 are shown in relation toFIG. 21C. As shown in 21C, the example radio network node 12 includes anantenna 1040, radio circuitry (e.g. radio front-end circuitry) 1010,processing circuitry 1020, and the radio network node 12 may alsoinclude a memory 1030. The memory 1030 may be separate from theprocessing circuitry 1020 or an integral part of processing circuitry1020. Antenna 1040 may include one or more antennas or antenna arrays,and is configured to send and/or receive wireless signals, and isconnected to radio circuitry (e.g. radio front-end circuitry) 1010. Incertain alternative embodiments, radio network node 12 may not includeantenna 1040, and antenna 1040 may instead be separate from radionetwork node 12 and be connectable to radio network node 12 through aninterface or port.

The radio circuitry (e.g. radio front-end circuitry) 1010 may comprisevarious filters and amplifiers, is connected to antenna 1040 andprocessing circuitry 1020, and is configured to condition signalscommunicated between antenna 1040 and processing circuitry 1020. Incertain alternative embodiments, radio network node 12 may not includeradio circuitry (e.g. radio front-end circuitry) 1010, and processingcircuitry 1020 may instead be connected to antenna 1040 withoutfront-end circuitry 1010.

Processing circuitry 1020 may include one or more of radio frequency(RF) transceiver circuitry, baseband processing circuitry, andapplication processing circuitry. In some embodiments, the RFtransceiver circuitry 1021, baseband processing circuitry 1022, andapplication processing circuitry 1023 may be on separate chipsets. Inalternative embodiments, part or all of the baseband processingcircuitry 1022 and application processing circuitry 1023 may be combinedinto one chipset, and the RF transceiver circuitry 1021 may be on aseparate chipset. In still alternative embodiments, part or all of theRF transceiver circuitry 1021 and baseband processing circuitry 1022 maybe on the same chipset, and the application processing circuitry 1023may be on a separate chipset. In yet other alternative embodiments, partor all of the RF transceiver circuitry 1021, baseband processingcircuitry 1022, and application processing circuitry 1023 may becombined in the same chipset. Processing circuitry 1020 may include, forexample, one or more central processing units (CPUs), one or moremicroprocessors, one or more application specific integrated circuits(ASICs), and/or one or more field programmable gate arrays (FPGAs).

The radio network node 12 may include a power source 1050. The powersource 1050 may be a battery or other power supply circuitry, as well aspower management circuitry. The power supply circuitry may receive powerfrom an external source. A battery, other power supply circuitry, and/orpower management circuitry are connected to radio circuitry (e.g. radiofront-end circuitry) 1010, processing circuitry 1020, and/or memory1030. The power source 1050, battery, power supply circuitry, and/orpower management circuitry are configured to supply radio network node12, including processing circuitry 1020, with power for performing thefunctionality described herein.

Those skilled in the art will appreciate that alternative modules,units, or other means may be included in the user equipment 14 and/orradio network node 12 for performing the methods of FIGS. 16A-19B.

FIG. 22A illustrates additional details of a network node 1100A (e.g., abase station or a core network node) in accordance with one or moreembodiments. As shown, the network node 1100A includes processingcircuitry 1120 and communication circuitry 1110. The communicationcircuitry 110 may be configured to transmit via one or more antennas140, e.g., in embodiments where the communication circuitry 1110comprises radio circuitry. The processing circuitry 1120 is configuredto perform processing described above, e.g., in FIGS. 17A and/or 19A,such as by executing instructions stored in memory 1130. The processingcircuitry 1120 in this regard may implement certain functional means orunits.

FIG. 22B illustrates a network node 1100B that according to otherembodiments implements various functional means or units, e.g., via theprocessing circuitry 1120 in FIG. 22A. These functional means or units,e.g., for implementing the method in FIG. 17A, include for instance agenerating module or unit 1150 for generating configuration informationindicating one or more parameters for a frequency hopping patternaccording to which the user equipment 14 is to generate each of thesymbol groups on a single tone during a different time resource, whereinthe frequency hopping pattern hops the random access preamble signal apseudo random frequency distance at one or more other symbol groups.Also included is a transmitted module or unit 1160 for transmitting theconfiguration information to the user equipment 14.

Those skilled in the art will also appreciate that embodiments hereinfurther include corresponding computer programs.

A computer program comprises instructions which, when executed on atleast one processor of a node, cause the node to carry out any of therespective processing described above. A computer program in this regardmay comprise one or more code modules corresponding to the means orunits described above.

Embodiments further include a carrier containing such a computerprogram. This carrier may comprise one of an electronic signal, opticalsignal, radio signal, or computer readable storage medium.

In this regard, embodiments herein also include a computer programproduct stored on a non-transitory computer readable (storage orrecording) medium and comprising instructions that, when executed by aprocessor of a (transmitting or receiving) radio node, cause the radionode to perform as described above.

Embodiments further include a computer program product comprisingprogram code portions for performing the steps of any of the embodimentsherein when the computer program product is executed by a computingdevice. This computer program product may be stored on a computerreadable recording medium.

Still further embodiments herein include the following enumeratedembodiments.

As shown in FIG. 23A, a first enumerated embodiment includes a method1200 implemented by a wireless communication device in a wirelesscommunication system for transmitting a random access preamble signal,the method comprising: generating a random access preamble signal thatcomprises multiple symbol groups, with each symbol group on a singletone during a different time resource, according to a frequency hoppingpattern that hops the single tone a fixed frequency distance at one ormore symbol groups and hops the single tone one of multiple differentpossible frequency distances (e.g., a pseudorandom frequency distance)at one or more other symbol groups, wherein each symbol group comprisesone or more symbols (Block 1210); and transmitting the random accesspreamble signal (Block 1220).

A second enumerated embodiment includes the method of the firstenumerated embodiment, further comprising randomly selecting a singletone on which to generate a first one of the multiple symbol groups, andselecting to hop the single tone on which to generate subsequent ones ofthe multiple symbol groups according to the frequency hopping pattern.

As shown in FIG. 23B, a third enumerated embodiment includes a method1300 implemented by a radio network node in a wireless communicationsystem for receiving a random access preamble signal, the methodcomprising: receiving a signal from a wireless communication device(Block 1310); and processing the received signal in an attempt to detecta random access preamble that comprises multiple symbol groups, witheach of the symbol groups on a single tone during a different timeresource, according to a frequency hopping pattern that hops the singletone a fixed frequency distance at one or more symbol groups and hopsthe single tone one of multiple different possible frequency distances(e.g., a pseudorandom frequency distance) at one or more other symbolgroups, wherein each symbol group comprises one or more symbols (Block1320).

A fourth enumerated embodiment includes the method of the thirdenumerated embodiment, further comprising receiving one or more othersignals from one or more other wireless communication devices, andprocessing the one or more other signals in an attempt to detect one ormore other random access preambles multiplexed in frequency with therandom access preamble, according to different frequency hoppingpatterns.

As shown in FIG. 24A, a fifth enumerated embodiment includes a method1400 implemented by a network node in a wireless communication systemfor configuring a wireless communication device to transmit a randomaccess preamble signal comprising multiple symbol groups, each symbolgroup comprising one or more symbols, the method comprising: generatingconfiguration information indicating one or more parameters for afrequency hopping pattern according to which the wireless communicationdevice is to generate each of the symbol groups on a single tone duringa different time resource, wherein the frequency hopping pattern hopsthe single tone a fixed frequency distance at one or more symbol groupsand hops the single tone one of multiple different possible frequencydistances (e.g., a pseudorandom frequency distance) at one or more othersymbol groups (Block 1410); and transmitting the configurationinformation to the wireless communication device (Block 1420).

A sixth enumerated embodiment includes the method of the fifthenumerated embodiment, further comprising configuring multiple differentfrequency bands in which random access preamble signals for differenttypes of wireless communication devices are to be transmitted, whereinthe different frequency bands have different numbers of tones therein.

A seventh enumerated embodiment includes the method of any of the fifththrough sixth enumerated embodiments, wherein the configurationinformation indicates at least one parameter indicating in which bandthe wireless communication device is to transmit a random accesspreamble signal and/or a number of tones in the band.

An eighth enumerated embodiment includes the method of any of the firstthrough seventh enumerated embodiments, wherein the fixed frequencydistances is less than or equal to a frequency distance thresholdassociated with a targeted cell size and/or a targeted time-of-arrivalestimation range, and at least one of the multiple different possiblefrequency distances is greater than the frequency distance threshold.

A ninth enumerated embodiment includes the method of the eighthenumerated embodiment, wherein the frequency distance threshold is afrequency distance spanned by one tone.

A tenth enumerated embodiment includes the method of the eighthenumerated embodiment, wherein the frequency distance threshold is afrequency distance spanned by two tones.

An eleventh enumerated embodiment includes the method of any of thefirst through tenth enumerated embodiments, wherein the multipledifferent possible frequency distances comprise pseudo-randomlygenerated frequency distances.

A twelfth enumerated embodiment includes The method of any of the firstthrough eleventh enumerated embodiments, wherein the frequency distanceto hop at each of said one or more other symbol groups is pseudorandomly selected from among the multiple different possible frequencydistances.

A thirteenth enumerated embodiment includes the method of any of thefirst through twelfth enumerated embodiments, wherein the frequencyhopping pattern hops the single tone a fixed frequency distance at eachsymbol group in a first set of one or more symbol groups, and hops thesingle tone one of multiple different possible frequency distances ateach symbol group in a second set of one or more symbol groups differentthan the first set.

A fourteenth enumerated embodiment includes the method of any of thefirst through thirteenth enumerated embodiments, wherein the frequencyhopping pattern comprises a combination of a fixed distance hoppingpattern and a multi-distance hopping pattern, wherein the fixed distancehopping pattern hops the single tone a fixed frequency distance at eachsymbol group in a first set of one or more symbol groups, and themulti-distance hopping pattern hops the single tone one of multipledifferent possible frequency distances at each symbol group in a secondset of one or more symbol groups different than the first set.

A fifteenth enumerated embodiment includes the method of the fourteenthenumerated embodiment, wherein the multi-distance hopping pattern is apseudo-random hopping pattern.

A sixteenth enumerated embodiment includes the method of any of thethirteenth through fifteenth enumerated embodiment, wherein the symbolgroups in the first and second sets are interlaced in time and arenon-overlapping, with both the first and second sets including everyother symbol group.

A seventeenth enumerated embodiment includes the method of any of thethirteenth through sixteenth enumerated embodiments, wherein a frequencydistance hopped at a symbol group in the second set is selected fromcandidate frequency distances that include 0, 1, . . . and N_(b) ^(sc)−1multiples of a frequency distance spanned by a single tone, whereinN_(b) ^(sc) is a number of tones in a transmission bandwidth of therandom access preamble signal.

An eighteenth enumerated embodiment includes the method of any of thethirteenth through sixteenth enumerated embodiments, wherein a frequencydistance hopped at a symbol group in the second set is selected fromcandidate frequency distances that include 0, N_(sb) ^(sc), 2N_(sb)^(sc), . . . , and N_(b) ^(sc)−N_(sb) ^(sc), multiples of a frequencydistance spanned by a single tone, wherein N_(b) ^(sc) is a number oftones in a transmission bandwidth of the random access preamble signal,wherein N_(sb) ^(sc) is a number of tones in any given subband.

A nineteenth enumerated embodiment includes the method of any of thefirst through eighteenth enumerated embodiments, wherein the fixeddistance hopping pattern hops the single tone the fixed frequencydistance at a symbol group in a direction that depends on a frequencylocation of the symbol group.

A twentieth enumerated embodiment includes the method of any of thefirst through eighteenth enumerated embodiments, wherein the fixeddistance hopping pattern hops the single tone the fixed frequencydistance at each symbol group in the same direction.

A twenty-first enumerated embodiment includes the method of any of thefirst through twentieth enumerated embodiments, wherein the frequencyhopping pattern hops the single tone across a transmission bandwidth ofthe random access preamble signal, such that the multiple symbol groupsspan the transmission bandwidth.

A twenty-second enumerated embodiment includes the method of any of thefirst through twenty-first enumerated embodiments, wherein a timeresource comprises an Orthogonal Frequency Division Multiplexing symbolgroup interval.

A twenty-third enumerated embodiment includes the method of any of thefirst through twenty-second enumerated embodiments, wherein a tone is anOrthogonal Frequency Division Multiplexing subcarrier.

A twenty-fourth enumerated embodiment includes the method of any of thefirst through twenty-third enumerated embodiments, wherein the wirelesscommunication device is a narrowband Internet of Things (NB-IoT) device.

A twenty-fifth enumerated embodiment includes the method of any of thefirst through twenty-fourth enumerated embodiments, wherein the randomaccess preamble signal is transmitted over a narrowband Physical RandomAccess Channel (PRACH).

A twenty-sixth enumerated embodiment includes a wireless communicationdevice in a wireless communication system for transmitting a randomaccess preamble signal, the wireless communication device configured to:generate a random access preamble signal that comprises multiple symbolgroups, with each symbol group on a single tone during a different timeresource, according to a frequency hopping pattern that hops the singletone a fixed frequency distance at one or more symbol groups and hopsthe single tone one of multiple different possible frequency distancesat one or more other symbol groups, wherein each symbol group comprisesone or more symbols; and transmit the random access preamble signal.

A twenty-seventh enumerated embodiment includes the wirelesscommunication device of the twenty-sixth enumerated embodiment,configured to perform the method of any of the second and eight throughtwenty-fifth enumerated embodiments.

A twenty-eighth enumerated embodiment includes a wireless communicationdevice in a wireless communication system for transmitting a randomaccess preamble signal, the wireless communication device comprising: agenerating module for generating a random access preamble signal thatcomprises multiple symbol groups, with each symbol group on a singletone during a different time resource, according to a frequency hoppingpattern that hops the single tone a fixed frequency distance at one ormore symbol groups and hops the single tone one of multiple differentpossible frequency distances at one or more other symbol groups, whereineach symbol group comprises one or more symbols; and a transmittingmodule for transmitting the random access preamble signal.

A twenty-ninth enumerated embodiment includes a radio network node in awireless communication system for receiving a random access preamblesignal, the radio network node configured to: receive a signal from awireless communication device; and process the received signal in anattempt to detect a random access preamble that comprises multiplesymbol groups, with each of the symbol groups on a single tone during adifferent time resource, according to a frequency hopping pattern thathops the single tone a fixed frequency distance at one or more symbolgroups and hops the single tone one of multiple different possiblefrequency distances at one or more other symbol groups, wherein eachsymbol group comprises one or more symbols.

A twenty-ninth enumerated embodiment includes a radio network node ofthe twenty-ninth enumerated embodiment, configured to perform the methodof any of the fourth and eighth through twenty-fifth enumeratedembodiments.

A thirtieth enumerated embodiment includes a radio network node in awireless communication system for receiving a random access preamblesignal, the radio network node comprising: a receiving module forreceiving a signal from a wireless communication device; and aprocessing module for processing the received signal in an attempt todetect a random access preamble that comprises multiple symbol groups,with each of the symbol groups on a single tone during a different timeresource, according to a frequency hopping pattern that hops the singletone a fixed frequency distance at one or more symbol groups and hopsthe single tone one of multiple different possible frequency distancesat one or more other symbol groups, wherein each symbol group comprisesone or more symbols.

A thirty-second enumerated embodiment includes a network node in awireless communication system for configuring a wireless communicationdevice to transmit a random access preamble signal comprising multiplesymbol groups, each symbol group comprising one or more symbols, thenetwork node configured to: generate configuration informationindicating one or more parameters for a frequency hopping patternaccording to which the wireless communication device is to generate eachof the symbol groups on a single tone during a different time resource,wherein the frequency hopping pattern hops the single tone a fixedfrequency distance at one or more symbol groups and hops the single toneone of multiple different possible frequency distances at one or moreother symbol groups; and transmit the configuration information to thewireless communication device.

A thirty-third enumerated embodiment includes a network node of thethirty-second enumerated embodiment, configured to perform the method ofany of the sixth through twenty-fifth enumerated embodiments.

A thirty-fourth enumerated embodiment includes a network node in awireless communication system for configuring a wireless communicationdevice to transmit a random access preamble signal comprising multiplesymbol groups, each symbol group comprising one or more symbols, thenetwork node comprising: a generating module for generatingconfiguration information indicating one or more parameters for afrequency hopping pattern according to which the wireless communicationdevice is to generate each of the symbol groups on a single tone duringa different time resource, wherein the frequency hopping pattern hopsthe single tone a fixed frequency distance at one or more symbol groupsand hops the single tone one of multiple different possible frequencydistances at one or more other symbol groups; and a transmitting modulefor transmitting the configuration information to the wirelesscommunication device.

A thirty-fifth enumerated embodiment includes a computer programcomprising instructions which, when executed by at least one processorof a node, causes the node to perform the method of any of the firstthrough twenty-fifth enumerated embodiments.

A thirty-sixth enumerated embodiment includes a carrier containing thecomputer program of the thirty-fifth enumerated embodiment, wherein thecarrier is one of an electronic signal, optical signal, radio signal, orcomputer readable storage medium.

As shown in FIG. 24B, another embodiment includes a method 1500implemented by a wireless communication device in a wirelesscommunication system for configuring the wireless communication deviceto transmit a random access preamble signal comprising multiple symbolgroups, each symbol group comprising one or more symbols, the methodcomprising: receiving configuration information indicating one or moreparameters for a frequency hopping pattern according to which thewireless communication device is to generate each of the symbol groupson a single tone during a different time resource, wherein the frequencyhopping pattern hops the single tone a fixed frequency distance at oneor more symbol groups and hops the single tone one of multiple differentpossible frequency distances (e.g., a pseudorandom frequency distance)at one or more other symbol groups (Block 1510); and configuring thewireless communication device to generate the random access signalaccording to the received configuration information (Block 1520).

Those skilled in the art will recognize that the present invention maybe carried out in other ways than those specifically set forth hereinwithout departing from essential characteristics of the invention. Thepresent embodiments are thus to be considered in all respects asillustrative and not restrictive.

What is claimed is:
 1. A user equipment configured for use in a wirelesscommunication system, the user equipment comprising: processingcircuitry and radio circuitry, whereby the user equipment is configuredto: generate a random access preamble signal that comprises multiplesymbol groups, with each symbol group on a single tone during adifferent time resource, according to a frequency hopping pattern thathops the random access preamble signal from at least one of the symbolsgroups to an adjacent symbol group over a fixed frequency distance andhops the random access preamble signal from at least one of the symbolsgroups to an adjacent symbol group over a pseudo random frequencydistance, wherein each symbol group in the random access preamble signalcomprises one or more symbols; and transmit the random access preamblesignal.
 2. The user equipment of claim 1, configured to randomly selecta single tone on which to transmit a first one of the multiple symbolgroups, and select the single tones on which to respectively transmitsubsequent ones of the multiple symbol groups according to the frequencyhopping pattern.
 3. The user equipment of claim 1, wherein the pseudorandom frequency distance is a function of a cell identity.
 4. The userequipment of claim 1, wherein the fixed frequency distance comprises afrequency distance of a single tone.
 5. The user equipment of claim 1,wherein each symbol group in the random access preamble signal comprisesa cyclic prefix and two or more symbols.
 6. The user equipment of claim1, wherein each symbol group in the random access preamble signalcomprises a cyclic prefix and five identical symbols.
 7. The userequipment of claim 1, wherein the frequency hopping pattern hops therandom access preamble signal from at least one of the symbols groups toan adjacent symbol group over a fixed frequency distance in a directionthat depends on a frequency location of the at least one of the symbolgroups.
 8. The user equipment of claim 1, wherein each of the differenttime resources comprises a single-carrier frequency-divisionmultiple-access (SC-FDMA) symbol group interval.
 9. The user equipmentof claim 1, wherein each of the single tones on which the symbol groupsare generated is a single-carrier frequency-division multiple-access(SC-FDMA) subcarrier.
 10. The user equipment of claim 1, wherein theuser equipment is a narrowband Internet of Things (NB-IoT) device. 11.The user equipment of claim 1, wherein the random access preamble signalis transmitted over a narrowband Physical Random Access Channel,NB-PRACH.
 12. A radio network node configured for use in a wirelesscommunication system, the radio network node comprising: processingcircuitry and radio circuitry, wherein the radio network node isconfigured to: receive a signal from a user equipment; and process thereceived signal in an attempt to detect a random access preamble signalthat comprises multiple symbol groups, with each of the symbol groups ona single tone during a different time resource, according to a frequencyhopping pattern that hops the random access preamble signal from atleast one of the symbols groups to an adjacent symbol group over a fixedfrequency distance and hops the random access preamble signal from atleast one of the symbols groups to an adjacent symbol group over apseudo random frequency distance, wherein each symbol group in therandom access preamble signal comprises one or more symbols.
 13. Theradio network node of claim 12, further configured to receive one ormore other signals from one or more other user equipments, and processthe one or more other signals in an attempt to detect one or more otherrandom access preamble signals multiplexed in frequency with the randomaccess preamble signal, according to different frequency hoppingpatterns.
 14. The radio network node of claim 12, wherein the pseudorandom frequency distance is a function of a cell identity.
 15. Theradio network node of claim 12, wherein the fixed frequency distancecomprises a frequency distance of a single tone.
 16. The radio networknode of claim 12, wherein each symbol group in the random accesspreamble signal comprises a cyclic prefix and two or more symbols. 17.The radio network node of claim 12, wherein each symbol group in therandom access preamble signal comprises a cyclic prefix and fiveidentical symbols.
 18. The radio network node of claim 12, wherein thefrequency hopping pattern hops the random access preamble signal from atleast one of the symbols groups to an adjacent symbol group over a fixedfrequency distance in a direction that depends on a frequency locationof the at least one of the symbol groups.
 19. The radio network node ofclaim 12, wherein each of the different time resources comprises asingle-carrier frequency-division multiple-access (SC-FDMA) symbol groupinterval.
 20. The radio network node of claim 12, wherein each of thesingle tones on which the symbol groups are generated is asingle-carrier frequency-division multiple-access (SC-FDMA) subcarrier.21. The radio network node of claim 12, wherein the user equipment is anarrowband Internet of Things (NB-IoT) device.
 22. The radio networknode of claim 12, wherein the random access preamble signal istransmitted over a narrowband Physical Random Access Channel, NB-PRACH.23. A method implemented by a user equipment configured for use in awireless communication system, the method comprising: generating arandom access preamble signal that comprises multiple symbol groups,with each symbol group on a single tone during a different timeresource, according to a frequency hopping pattern that hops the randomaccess preamble signal from at least one of the symbols groups to anadjacent symbol group over a fixed frequency distance and hops therandom access preamble signal from at least one of the symbols groups toan adjacent symbol group over a pseudo random frequency distance,wherein each symbol group in the random access preamble signal comprisesone or more symbols; and transmitting the random access preamble signal.24. The method of claim 23, further comprising randomly selecting asingle tone on which to transmit a first one of the multiple symbolgroups, and selecting the single tones on which to respectively transmitsubsequent ones of the multiple symbol groups according to the frequencyhopping pattern.
 25. The method of claim 23, wherein the pseudo randomfrequency distance is a function of a cell identity.
 26. The method ofclaim 23, wherein the fixed frequency distance comprises a frequencydistance of a single tone.
 27. The method of claim 23, wherein eachsymbol group in the random access preamble signal comprises a cyclicprefix and two or more symbols.
 28. The method of claim 23, wherein eachsymbol group in the random access preamble signal comprises a cyclicprefix and five identical symbols.
 29. The method of claim 23, whereinthe frequency hopping pattern hops the random access preamble signalfrom at least one of the symbols groups to an adjacent symbol group overa fixed frequency distance in a direction that depends on a frequencylocation of the at least one of the symbol groups.
 30. A methodimplemented by a radio network node configured for use in a wirelesscommunication system, the method comprising: receiving a signal from auser equipment; and processing the received signal in an attempt todetect a random access preamble that comprises multiple symbol groups,with each of the symbol groups on a single tone during a different timeresource, according to a frequency hopping pattern that hops the randomaccess preamble signal from at least one of the symbols groups to anadjacent symbol group over a fixed frequency distance and hops therandom access preamble signal from at least one of the symbols groups toan adjacent symbol group over a pseudo random frequency distance,wherein each symbol group in the random access preamble signal comprisesone or more symbols.